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CN-121990791-A - Double-nano low-density thixotropic cement paste system and application thereof

CN121990791ACN 121990791 ACN121990791 ACN 121990791ACN-121990791-A

Abstract

A double-nanometer low-density thixotropic cement paste system relates to the technical field of oil and gas well drilling engineering and solves the problem that the existing cement paste system is difficult to be suitable for stratum with low pore pressure and serious leakage. The cement slurry system comprises, by weight, 40-60 parts of G-grade oil well cement, 14-25 parts of a solid lightening agent, 20-45 parts of a solid external admixture, 3-6 parts of a solid thixotropic agent, 0.5-2 parts of a nano stabilizer, 1-3 parts of a nano early strength agent, 1-3 parts of a fluid loss agent, 0.5-1 part of a dispersing agent and 70-100 parts of water. The double-nanometer low-density thixotropic cement paste system has the characteristics of lower density, high thixotropy and short waiting time, can effectively stay in a shaft of a cement plug with lower density in cement paste, quickly form a gel structure due to high thixotropy, has controllable compressive strength, is beneficial to drilling the plug, shortens waiting time and saves production cost, thereby achieving the production aims of high-efficiency plugging, quality improvement and efficiency improvement.

Inventors

  • ZHAI XIANGYU
  • JIANG ZENGDONG
  • WANG HUAN
  • YANG XIUTIAN
  • WEI YIXUN
  • GAO QING
  • HOU LIWEI
  • SONG YANTAO
  • WANG GUANGLEI
  • WANG XUGUANG
  • LI NA
  • XIANG YUANLONG
  • PAN YONGQIANG
  • ZHENG QINGYOU

Assignees

  • 大庆钻探工程有限公司
  • 中国石油天然气集团有限公司

Dates

Publication Date
20260508
Application Date
20250916

Claims (14)

  1. 1. A double-nanometer low-density thixotropic cement paste system is characterized by comprising the following components in parts by weight: 40-60 parts of G-level oil well cement, 14-25 parts of solid lightening agent, 20-45 parts of solid external admixture, 3-6 parts of solid thixotropic agent, 0.5-2 parts of nano stabilizer, 1-3 parts of nano early strength agent, 1-3 parts of fluid loss agent, 0.5-1 part of dispersing agent and 70-100 parts of water.
  2. 2. The dual nano low-density thixotropic cement paste system according to claim 1, wherein said solid lightening agent comprises hollow glass beads and vitrified perlite; The weight ratio of the hollow glass beads to the vitrified perlite is 20-40:60-80; The density of the hollow glass beads is 0.39-0.42g/cm 3 , and the specific surface area is 0.2-2m 3 /g; The density of the vitrified perlite is 0.80-1.20g/cm 3 , and the specific surface area is 1-3m 3 /g.
  3. 3. The double-nano low-density thixotropic cement paste system according to claim 1, wherein the solid external admixture comprises fly ash, slag powder and micro-silicon, and the weight ratio of the fly ash to the slag powder to the micro-silicon is 40-60:15-25:20-50.
  4. 4. The thixotropic cement paste system with double nano-levels and low density according to claim 3, wherein the coal ash is a secondary coal ash, the specific surface area is more than 300m 3 /kg, and the loss on ignition is less than 8%; the slag powder is of S95 grade, and the specific surface area is 400-500m 3 /kg; the content of the micro silicon density 1.20g/cm 3 ,SiO 2 is more than 85%, and the grain diameter is 0.1-0.3 mu m.
  5. 5. The dual-nano low-density thixotropic cement paste system according to claim 1, wherein the solid thixotropic agent comprises attapulgite and sulfate, and the weight ratio of the attapulgite to the sulfate is 40-50:50-60.
  6. 6. The double-nano low-density thixotropic cement paste system according to claim 5, wherein the attapulgite has a gel number of 55-60ml/15g and a specific surface area of 400-500m 3 /g; the sulfate is one or more of aluminum sulfate, sodium sulfate and calcium sulfate.
  7. 7. The double-nano low-density thixotropic cement paste system according to claim 1 is characterized in that the nano stabilizer is hydrophilic nano silicon dioxide with the particle size of 10-100nm, the fluid loss agent is AMPS fluid loss agent, and the dispersing agent is comb-type polycarboxylic acid dispersing agent.
  8. 8. The double-nano low-density thixotropic cement paste system according to claim 1, wherein the nano early strength agent is nano calcium silicate hydrate early strength agent with the particle size of 10-100nm; The composition of the composite material is that the weight ratio of the soluble calcium salt to the soluble silicate to the dispersing agent to the coupling agent is 30-45:25-45:20-30:5-10.
  9. 9. The dual-nano low-density thixotropic cement paste system of claim 8 wherein said soluble calcium salt is at least one of calcium nitrate tetrahydrate and calcium formate and said soluble silicate is at least one of sodium metasilicate pentahydrate and sodium metasilicate nonahydrate.
  10. 10. The dual-nano low-density thixotropic cement paste system according to claim 8, wherein the coupling agent is one or more of polyvinyl alcohol, polyvinylpyrrolidone, polyethylene glycol or sodium dodecyl benzene sulfonate, and the dispersing agent is a comb-type polycarboxylic acid dispersing agent.
  11. 11. The double-nano low-density thixotropic cement paste system according to claim 8, wherein the preparation method of the nano-scale hydrated calcium silicate early strength agent comprises the following steps: preparing a dispersing agent and a coupling agent into a first solution; Preparing a second solution of soluble calcium salt and a third solution of soluble silicate; Simultaneously dropwise adding the second solution and the third solution into the first solution under the continuous stirring state and the nitrogen atmosphere, controlling the dropwise adding system to be dropwise added for a set time under the set temperature condition, and continuously stirring the dropwise adding system for a set time under the same temperature condition to obtain a hybrid suspension; And (3) after centrifugal filtering and washing treatment and drying treatment are carried out on the hybrid suspension, grinding the obtained particles into solid nano-scale hydrated calcium silicate.
  12. 12. The double-nano low-density thixotropic cement paste system according to claim 11, wherein the first solution is obtained by preparing a dispersing agent into a solution with the mass concentration of 10-15%, adding a coupling agent, uniformly stirring, and adjusting the pH value to be between 11.0 and 13.5; the second solution is a soluble calcium salt solution with the mass concentration of 10-20%, the third solution is a soluble silicate solution with the mass concentration of 10-20%, and the molar ratio of calcium ions to silicate ions is 1:1-1.75:1.
  13. 13. The double-nanometer low-density thixotropic cement paste system according to claim 11, wherein the rotation speed of continuous stirring is 700 rpm-7000 rpm, the set temperature of the dropwise adding system is 20-40 ℃, the set time of dropwise adding is 3-5 h, the second solution and the third solution are simultaneously dripped, the pH value of the dropwise adding system is controlled to be 11.0-13.5 in the dropwise adding process, and the set time of continuous stirring of the dropwise adding system is 1d; The drying treatment method is that the drying is carried out for 1d under the condition that the temperature of a vacuum drying oven is 50-70 ℃, and then the drying is carried out for 2h at normal temperature in a dryer.
  14. 14. Use of a dual nano low density thixotropic cement paste system according to any one of claims 1 to 13 for lost circulation operations in the event of severe and malignant loss during drilling.

Description

Double-nano low-density thixotropic cement paste system and application thereof Technical Field The invention relates to the technical field of oil and gas well drilling engineering, in particular to a double-nano low-density thixotropic cement paste system and application thereof. Background In the drilling process, stratum leakage is a common complex problem, especially in crack development, karst cave property and low-pressure stratum, the drilling fluid leakage is serious, the drilling efficiency is reduced, the cost is increased, and even safety accidents such as well wall instability and the like can be possibly caused. The traditional plugging technology is to perform plugging by bridging a plugging material and a gel material through drilling fluid, wherein the traditional Chinese patent 'a plugging and leakage-preventing drilling fluid material and a using method thereof' (publication No. CN 113773816A) discloses that the plugging and leakage-preventing drilling fluid material mainly comprises fiber materials, core-shell particles, plant shell particles, oil-soluble resins, porous materials, calcium carbonate, quartz sand and the like, the traditional Chinese patent 'a gel plugging agent and a preparation method thereof' (publication No. CN 105567190A) discloses a gel expansion plugging agent containing functional groups capable of enhancing interaction with stratum in molecules, and the retention capacity of the plugging material in a leakage layer is improved by chemical crosslinking in an aqueous solution polymerization mode. The method is more suitable for stratum with the leakage speed within 30m 3/h, has no obvious effect on stratum with serious leakage and complete leakage (return leakage) when the leakage speed exceeds 30m 3/h, for example, in the overseas irak Lu Maila area, the secondary drilling leakage layer contains porous dolomite or limestone, holes and cracks develop, and karst cave or karst cave-like structures exist. Conventional plugging slurry has poor plugging effect, and common cement slurry is used for plugging, but conventional density cement slurry has the problems of high density, poor thixotropy, difficult residence, high strength of cement stone, easy drilling of a new borehole and the like, and cannot effectively plug a leakage channel because the pore pressure of a plugging layer is 1.06-1.11g/cm 3. The research shows that the thixotropic cement paste has the characteristic of rapidly developing a shearing dilution and static gelation structure, and is more suitable for the situation of serious leakage of a shaft. In addition, the lower cement slurry density (cement slurry density is 1.20-1.30g/cm 3) can lead more cement plugs to reside in a shaft after the pressure in the leakage layer is balanced (plugging is successful), is beneficial to the plugging of the drilling plug, and is beneficial to grasping the actual plugging situation, the publication No. CN113429163A discloses a low-density plugging cement slurry, but the 24h compressive strength of the cement stone exceeds 10MPa, the cement stone strength is too high, the situation that the drilling plug deviates to form a new borehole easily occurs, and the addition of cement external admixtures (such as fly ash, slag and the like) can reduce the early strength, but the waiting time is greatly prolonged, and the plugging efficiency is affected. Thus, for formations with low pore pressure and severe leakage, there is a need for a cement slurry system that combines lower density, high thixotropic properties, and short waiting times. Disclosure of Invention The invention provides a double-nanometer low-density thixotropic cement paste system, which aims at solving the problems that the conventional cement paste system in the background technology is difficult to be suitable for stratum with low pore pressure and serious leakage. The double-nanometer low-density thixotropic cement paste system has the characteristics of lower density, high thixotropy and short waiting time, can effectively stay in a shaft when a cement paste achieves a cement plug with lower density (cement paste density is 1.20-1.30g/cm 3), has high thixotropic property and rapidly forms a gel structure, has controllable compressive strength, is beneficial to drilling the plug, shortens waiting time and saves production cost, thereby achieving the production aims of high-efficiency plugging and quality and efficiency improvement. The invention also provides an application of the double-nanometer low-density thixotropic cement paste system. The invention solves the problems by the following technical scheme that the double-nanometer low-density thixotropic cement paste system comprises the following components in parts by weight: 40-60 parts of G-level oil well cement, 14-25 parts of solid lightening agent, 20-45 parts of solid external admixture, 3-6 parts of solid thixotropic agent, 0.5-2 parts of nano stabilizer, 1-3 parts of nano early strength agent